A scanning system makes use of focusing a reflecting light beam through a photodetector to generate an image signal for further image processing. A conventional scanner system includes a light source, a mirror, and a lens set, which are used to guide the reflecting light to a charge couple device (CCD). The charge couple device is utilized to generate an image signal. A pre-processing element is used to respond an image signal and adjust dc gain of the image signal. An analogue to digital converter is used to convert adjusted image signal to a digital signal and a post-processing element to generate an image code by processing said digital signal through highlight, shadow, and Gamma correction.
Image capture is achieved by passing the document in front of a device known as a CCD. This consists of a lot of very small, individual semiconductor receptors, disposed in a linear array. The document is passed in front of the CCD and a complete image of the document linear segments individually captured from the CCD. The CCD consists of a semiconductor material which is formulated to convert incident light into an analogue electrical signal. Therefore, the alignment of the CCD is very important in the scanning system.
In practicing the scanning system, the light source is reflected from the surface of a document, then it is reflected against from the mirror and focused by a lens set. The mirror and the lens set are used to guide the light beam to a CCD. Subsequently, the light beam is converted to an image signal by the CCD, and direct current (d.c.) gain of the image signal is adjusted by a pre-processing element, i.e. a d.c. gain voltage amplifier. Then the adjusted image is fed to an analogue to digital converter (ADC) for converting adjusted image signal to a digital signal. The digital signal is fed to a post-processing element to generate an image code by processing the digital signal through highlight, shadow, and Gamma correction.
Turning to FIG. 1, it shows a conventional alignment pattern 1. Typically, the alignment pattern 1 has three pairs of fixer 3A, 3B and 3C formed on the edges of the alignment pattern to fix the alignment pattern during fine alignment, rough alignment and resolution analysis, respectively. A fine horizontal pattern 5 is formed on the upper portion of the alignment pattern 1 to serve as a fine alignment pattern 5. A horizontal pattern 7 is formed on the central portion of the alignment pattern 1 for acting as a rough alignment pattern 7. A pair of discontinuous regions 9 are formed near the terminations of the rough alignment pattern 7 to use as boundary alignment patterns 9. Further, a resolution analysis pattern 11 is formed on the lower portion of the alignment pattern 1. The resolution analysis pattern 11 is used to analyze the resolution of the scanning system. Typically, a plurality of fine lines 13 are repeatedly, vertically formed in the resolution analysis pattern 11 for analyzing the resolution of the scanning system. The distances between the fine lines 13 are equal.
Generally speaking, there are three steps to align the CCD of the scanning system known as a horizontal alignment, a boundary alignment and resolution analysis, respectively. Unfortunately, it is not very convenient for operating an alignment procedure by using the alignment pattern 1. It is because that the fixers 3A, 3B and 3C are respectively served for different function. In other word, the fixers of the alignment pattern 1 have to be frequently changed and adjusted for different CCD alignment procedure. Further, the operator does not know how to adjust the CCD to a correct area via an oscilloscope by using the pattern 1.